1. Field of the Invention
The present invention relates to a liquid crystal display apparatus, a manufacturing method thereof, and a liquid crystal projector using the liquid crystal display apparatus.
2. Description of the Related Art
In recent years, projection type image display apparatuses of the type using a reflection-type liquid crystal display called “LCOS (Liquid Crystal on Silicon) display” in the art of liquid crystal displays have been widespread. Such a projection-type image display apparatus is capable of displaying images that are smoother and have higher-definition and higher color reproducibility than projection-type image display apparatuses of the type using a transmission-type liquid crystal display.
Such liquid crystal displays as reflection-type liquid crystal displays of the LCOS type, in general, have a structure in which a liquid crystal member is held by peripheral sealing formed at a peripheral portion of the display and end sealing. A resin-sealing adhesive is typically used for both the peripheral sealing and the end sealing.
Such a resin-sealing adhesive calls for an essentially required property of preventing the liquid crystal member from leaking out of the liquid crystal display, as well as many other properties. Specifically, such properties include a property of failing to affect control of the gap between opposing substrates, a property of maintaining electro-optic characteristics of the liquid crystal display under a high-temperature and high-humidity environment, and a property of stabilizing liquid crystal alignment. Actually, however, a common resin-sealing adhesive used in the liquid-crystal-display manufacturing stage cannot completely prevent penetration of moisture under a high-temperature and high-humidity environment. Therefore, liquid crystal displays involve a problem with maintenance of the electro-optic characteristics under a high-temperature and high-humidity environment.
A reflection-type liquid crystal display of the LCOS type, in particular, has a transparent ITO electrode and a metal pixel electrode as opposing electrodes and, hence, the work functions of the two electrode materials are not equal to each other. Such an electrode configuration is called a variety-electrode configuration. With the variety-electrode configuration, it is conventionally known that positive ions and negative ions contained in the liquid crystal member are likely to become out of balance when a very small amount of moisture is mixed into the liquid crystal member.
Such imbalance of ions in the liquid crystal member leads to image retention. For this reason, preventing penetration of moisture is an important challenge for such a reflection-type liquid crystal display of the LCOS type in order to prevent image retention also.
Many techniques have been proposed to solve to the problem of moisture penetration into a liquid crystal display. For example, Japanese Patent Application Laid-Open No. S60-026321 has proposed a technique of forming a resin structure at a peripheral portion of a liquid crystal display.
Specifically, the technique described therein includes providing a double-structure sealing portion in which a low-water permeability resin (for example an epoxy adhesive) is used for a first sealing in contact with a liquid crystal layer, while a resin having a strong adhesion to a flexible substrate (for example a silicone adhesive) is used for an outer second sealing. Alternatively, the technique described therein includes providing a double-structure sealing portion in which a resin that has difficulty reacting with a liquid crystal (for example a silicone adhesive) is used for the first sealing in contact with the liquid crystal layer, while a low-water permeability resin (for example an epoxy adhesive) is used for the outer second sealing.
Japanese Patent Application Laid-Open No. S62-058221 has proposed a technique of depositing a metal oxide formed from an organic metal compound as a raw material over a moisture-penetration passage in order to improve the moisture resistance of a display apparatus under a high-temperature and high-humidity environment by leaps and bounds.